Thousands of folks, including 3 presidents, observed a moment of silence at Ground Zero to mark the exact moment when an American Airlines Jet slammed into one of the World Trade Center Twin Towers 20 years ago.
President Joe Biden, along with former Presidents Obama and Clinton, observed a moment of silence as people remembered the life-changing event 2 decades ago.
Nearly 3,000 people died as a result of the terrorist attack ... an assault on America that triggered the war on Afghanistan -- a war that many say went on way too long.
Various family members read the names of those who perished during the attack.
Bruce Springsteen took the podium and sang "I'll See You in My Dreams" as the crowd took it all in.
President Biden will leave New York City and visit the other 2 sites where the other 2 planes went down -- the Pentagon and a field in Shanksville, Pennsylvania.
President Obama has said in the lead-up to the anniversary, "One thing that became clear on 9/11 - and has been clear ever since - is that America has always been home to heroes who run towards danger in order to do what is right."
As you know, the attack was planned by al Qaeda leader Osama bin Laden, who was hunted down and killed during Obama's presidency. The U.S. government has maintained a secret file on Saudi Arabia's involvement in the attack, and after mounting pressure from family members of 2,000 people who perished ... President Biden said the document will be released, although he didn't say when.